Modulating gas heating control



Aug. 3, 1954 P. SCHELLv MODULATING GAS HEATING CONTROL Filed sept. 8,1951 f All QM. W

Patented Aug. 3, 1954 UNITED STATES TENT OFFICE Paul Schell, Elkhart,Ind., assignor to Penn Controls, Inc., Goshen, Ind., a corporation ofIndiana Application September 8, 1951, Serial No. 245,743

2 Claims. 1

This invention relates to a gas modulating heating control wherein amain gas valve of the modulating type having an on-ci seat and amodulating seat is provided, automatic control thereof being effected bya novel room thermostat, and circuit and pilot control devices in anovel conti-oi arrangement.

One object ol my present invention is to provide pilot control for amain gas valve of modulating type involving relatively simpleinstrumentalities which operate to control the ow of gas through the gasvalve by means of using the gas pressure itself acting on diaphragmethereof, the control instrumentalitics being in the form of valves whichare electrically operated, and a room thermostat being provided forcontrolling the flow of the electric current to the controlinstrumentalities in an eicient and foolproof manner.

Another object is to provide the room thermostat so arranged as to eiectmodulating control by reason of having primary and secondary contacts,one of which is carried by heat responsive actuator, the room thermostathaving a modulating heater for the actuator energized by closure of thecircuit through the Contact carried thereby to move said contact out ofengagement with its cooperating contact, the modulating heater beingheated as a result of closure of these contacts, and then, as a resultof opening of the contacts, cooling again and thus causing the heatresponsive actuator to produce a follow-up action that changes thefrequency and length of electrical impulses to a heater in one of theinstrumentalities for controlling the gas valve in a modulating mamier.

Still another object is to provide in combination with a modulating maingas valve having a diaphragm and chamber arrangement, a modulating pilotvalve for controlling the modulating action of the gas valve and athree-way valve for controlling the on-oi positioning of the main gasvalve.

A further object is to provide the modulating pilot valve and thethree-way valve electrically operable as by means of electric heaterswhich affect bimetal or similar warping elements, and then, in turnactuate the valves of the modulating pilot valve and the three-wayvalve, a room thermostat of modulating type being provided forcontrolling the energization of the heaters.

Still a further object is to provide a three- Way valve switch forcontrolling the actuating heater of the three-way valve so that itscircuit may be closed when a predetermined circuit of the roomthermostat is opened, and may be opened when said predetermined circuitof the room thermostat is closed for providing operation of thethree-way valve in response to the room thermostat when it responds totemperature rise.

An additional object is to provide a control of the character disclosedin which the modulating pilot valve is modulated by a modulating heaterarrangement of the room thermostat which senses temperature changes ofthe room and relays them in varying increments of electricalenergization of the actuating heater of the modulating pilot valve tocause it to modulate in .proportion to changes in room temperature andthus serve as a pilot to accurately modulate the main gas valve tosupply the proper amount of gas to the burner and result in maintainingthe temperature in the room substantially constant.

With these and other objects in View, my invention consists in theconstruction, arrangement and combination of the various parts of mymodulating gas heating control whereby the objects contemplated areattained, as hereinafter more fully set forth, pointed out in my claimsand illustrated in the accompanying drawings, wherein:

The gure is a diagrammatic showing of my gas modulating heating controlin which the valve structures are shown in cross section in g,mechanical part of the diagram and the circuits for them and for theroom thermostat are shown in an electro-diagrammatic portion of thefigure.

On the accompanying drawing I have used the reference character RT toindicate a room thermostat which is normally open as indicated (N. O.)following the designation RT. The room thermostat RT includes asecondary switch blade lll actuated by a biinetal coil ll responsive toroom temperature in the usual manner. Upon temperature rise the blade IGswings to the right as indicated by the arrow h indicating hot The roomthermostat is shown on the drawing in the non-normal or closed position.

The room thermostat RT comprises a primary blade l2 and a primarycontact I4 for coaction therewith, a secondary contact 8 being providedfor coaction with the secondary blade l0. In the cold position of theroom thermostat both blades l and l2 are separated from the respectivecontacts I6 and 4. Upon temperature rise the blade I2 engages thecontact I4 ahead of 3 engagement of the blade le with the contact i6.Primary and secondary, therefore, refer vto the order of closing of thecontacts |2| and IIB-I6.

The room thermostat further includes a heat responsive contact actuatorl5 on which the primary contact i4 is mounted. This actuator may be inthe form of a. bimetal blade which is somewhat more flexible than thebimetal and which, when heat is applied thereto as from a modulatingheater i8, will move in the direction of the arrow 7i crossing thebimetal blade and thus tend to separate the contact 4 from the contactI2 as soon as they are engaged and thereby again de-energize themodulating heater i8 as it is energized whenever the contacts i2 and lliare closed.

A three-way valve switch TWVS is provided having a switch actuator inthe form of a bimetal blade 22 and a Contact 24 for coaction therewith.The bimetal switch actuator 22 warps to the left when heated asindicated by the arrow h. For heating the blade a three-way valve switchheater 2D is provided. The contacts 22 and 24 of the three-way valveswitch are normally closed as indicated on the drawing by (N. C.)following the reference character TWVS.

At MGV a modulating main gas valve is indicated, the valve body of whichbears the reference numeral 25. The body 26 has an inlet 28 from the gassupply and an outlet 36 to the burner. Within the valve body an on-oivalve seat 32 is provided with which a valve disc 34 is normally engagedunder the action of a spring 46. Opposite the seat 32 is a modulatingvalve seat 36 and between these seats is an interseat chamber 35.

A valve stem 38 is connected with the valve disc 34 and seal-offdiaphragms 4D and 42 are connected therewith and with the valve body asiilustrated. The diaphragms provide rst and second chambers d8 and 56.The upper end of the valve stem 38 extends through a valve stem guide 44and the valve body may have means 52 to serve as a stop for the vaivestem 38 in a desirable minimum name position of the valve disc 34relative to the modulating seat 36.

Passageway means is provided in the valve body 26 at 54 and arestriction 56 therein causes 54 to constitute a restricted passagewaymeans to an oi seat 60 of a three-Way valve TWV having a body '59, andthrough a lateral passageway 55 to the rst chamber d'8 between thediaphragms 46 and 42. A passageway 53 is provided through the top of thevalve body 26 for communicating a passageway 62 of the three-way valveTWV with the second chamber 5U above the diaphragm 42.

The three-way valve TWV has a valve blade 64 of spring material carryinga valve disc 66. The blade 6d is so shaped as to normally seat the disc66 against an on seat 68 formed in the body 59 of the three-way valveTWV. A bleed-ofi connection i6 is provided from the on seat 68 to theburner chamber adjacent the burner therein.

A valve stem 'l2 is provided for actuating the valve disc 66 withrespect to the seats 60 and 68 and it is provided with a seal-offdiaphragm 'I4 to seal the seats 60, 62 and 68 relative to atmospherethrough that portion of the valve body 59 above the diaphragm, whichportion is in communication with atmosphere.

A valve return leaf spring 'I6 is provided for normally lifting thevalve stem T2 and an elec- 4 trically operated actuator is provided inthe form of a bimetal actuator 18 which, when heated, will war-pdownwardly and engage the valve return spring 16 to propel the stem Z2downwardly and close the valve disc 66 against the valve seat 66 afterseparating it from the seat 68. An electrically energizable actuatingheater is provided for the bimetal element and is shown at 66.

I provide manual resetting means for the three` way valve TWV whichconsists of a reset rod 82 having a fiange 84 thereon to coact with ahump 85 of the bimetal element T8 as will be hereinafter described. Areset knob 86 is provided on the rod 82 and a reset return spring 88encircles the rod under the knob.

The parts of the three-way valve TWV are normally in the position shownin the drawing and a legend following the reference character TWVindicates that the Valve disc 66 normally closes 62 with respect to 68and normally opens 62 with respect to 60.

The right hand side of the main gas valve body 26 is provided with apassageway S0 to the rst chamber 48 and a passageway 92 to the interseat chamber 35. A modulating pilot valve MPV (normally open) isprovided having a passageway from which a connection 94 leads to thepassageway 90, the body of the valve being indicated at Sl. This valvebody has therein a seat 98 connected by a conduit 96 to the passagewayS2. A valve disc |62 is mounted on a valve blade |60 which blade isbiased upwardly to space the disc |02 from the seat 98 and thereby open95 with respect to 98.

For closing the disc |02 against the seat 98 and for modulating the discrelative to the seat in the normally open position, I provide a bimetalvalve actuating blade |64, and an electrically energizable actuatingheater |06 is wound thereon for changing the position of the bimetalblade |04 in response to the duration and frequency of energization ofthe heater |66, as determined by the action of the room thermostat bladeI0 and the actuator I5 of the room thermostat.

The foregoing elements are connected in an electric circuit which mayinclude a step-down transformer T having a primary P and a secondary Sso that comparatively safe low voltage may be used for actuating thevarious elements of my control. The elements thus far described areconnected together with wires |08 to |34 as shown on the drawing andthese wires will be referred to specifically hereinafter when describingthe operation of the control.

Practical operation As shown on the drawing, the various parts of mycontrol are in the position which they assume as a result of the roomthermostat RT being satised. The three-way valve switch heater 2|) isenergized through the elements |08, H6, (20), |34, |6, I0, |22 and |20.The bimetal blade 22 thereof is accordingly in position for opening thecircuit of the heater 80 of the three-way valve TWV. The valve thereforeis in the normal position which results in the modulating gas valve MGVbeing closed (disc 34 against on-oi seat 32). This results from gasthrough the restricted passageway means 54-56 iiowing through 60, 62 and58 into the second chamber 50, thus balancing the pressure in thischamber with respect to the pressure through 55 in the first chamber 48.The spring 46 is therefore effective to hold the valve disc 34 closedagainst the seat 32.

Since the primary contacts |2 and |4 of the |22 and |20.

room thermostat RT are closed, the heater |06 of the modulating pilotvalve MPV is energized through |08, H0, II2 (|06), II4, I8, I4, I2, I0,II, The valve disc |02 is therefore seated against the seat 98 to cutolf communication between the interseat chamber 35 and the rst chamber48 of the main gas Valve.

As the room temperature goes down, the bimetal I I of the roomthermostat will unwind and swing the blade I toward the left thusbreaking the circuit at IIE-I6 (the secondary contacts) of the roomthermostat` 'I'his deenergizes the heater 20 so that the three-way Valveswitch TWVS will close a circuit through its contacts 22 and 24. This isthe circuit for the heater 80 through |08, IIIl, IIB, (80), |32, 24, 22,|28 and |20.

As the heater 80 heats up, it Warps the bimetal blade 'I8 downwardlyagainst the upward bias of the valve return spring 'I6 thus driving thestem I2 downwardly and transferring the valve disc 66 from the on seat68 to the off" seat B0. This cuts off the flow of gas from thepassageway 54 through 50, 62 and 58 to the second chamber 50 of the maingas valve and opens this chamber through 58, Sii, and 68 to thebleed-off connection '|0. The gas under pressure in the chamber 50 istherefore bled olf to reduce this chamber to substantially atmosphericpressure so that the pressure from the inlet 28 under the diaphragm 40and through the restricted passage means 54-56 and the lateralpassageway 55 to the primary chamber 48 under the diaphragm 42 willresult in upward movement of the valve stem 38 to open the gas valvedisc 34 relative to the onoif seat 32 and bring it adjacent but spacedfrom the modulating seat 36 as determined by the minimum flame stop 52.The modulating gas valve is now open so that gas through the burnerflows through the valve and of course is ignited in any suitable mannerat the burner.

Assuming that the room temperature will continue to lower and after afractional degree of temperature drop will open the room thermostat atthe primary contacts |2-|4. This permits deenergization of themodulating heater. The heater |06 of the modulating pilot valve MPV isthereby de-energized and the bimetal element |04 thereof will begin towarp upwardly for opening the valve disc |02 with respect to the valveseat S8. This permits bleed-on of the pressure in the first chamber 40of the modulating gas valve to the interseat chamber 35 from which itows into the burner chamber to be disposed of by burning therein.

Reduction of pressure in the chamber 48 will permit the discI 34 to moveaway from the modulating seat 36 and the degree of such movement will bedependent upon the degree of opening of the disc |02 relative to theseat 98 of the modulating pilot valve. The passageways 90, 94, 95, 98,98 and 82 for this purpose are larger than the restriction 5E so as tolet the gas under pressure out of the chamber 48 faster than it entersfrom the intake 28 if the gas valve is to be modulated to a wider openposition. On the other hand, if it is to be modulated to a more closedposition with relation to the seat 36, the valve |02 restricts the iiowfrom 90 to 92 more than it restricts 56, the position of the valve disc|02 being dependent on the position or degree of warping of the bimetalelement |04.

As soon as the contacts I2 and I 4 are separated, the flow of currentthrough the modulating heater I 8 is also discontinued so that thebimetal actuator I5 will be cooled by the surrounding atmosphere in theroom thermostat and will close I4 against I2 even though the roomtemperature is dropping. Reclosure of I2 and I4 re-energizes themodulating heater I8 and the heater |05 of the modulating pilot valve sothat they receive a shot of current and therefore tend to warp towardthe right and downwardly again respectively during the short period ofenergization of their heaters. The energization of the heater |06 issuch that it adds or reduces the heat affecting thc bimetal |04 in theinverse ratio to the requirements of the space being heated.

The contacts in the room thermostat are of the walking type which meansthat more or less heat can be added to the bimetal I 04 by very slighteffects of room temperature on the room thermostat. The greater theperiod of energization of the heater |06, the more nearly closed will bethe modulating pilot valve and likewise the more open will be themodulating gas valve (its valve disc 34 relative to the modulating seat36).

The alternate openings and closings of the primary contacts |2 and I4are repeated periodically with a rapidity depending upon the demand forheat as indicated by the bimetal II. This action causes proportionalamounts of heat in the heaters I and |06 to affect the bimetal elementsi5 and |04 so that varying amounts of heat are supplied to control themodulating pilot valve as directed by the bimetal II of the roomthermostat. As the circuit is arranged in my disclosure, a lesser amountof heat is supplied to these heaters as room temperature lowers.

As the bimetal II is aected by a rising room temperature and movestoward the modulating actuator I5, it raises the amount of heat suppliedto the heater |06 and thus reduces the ilame at the main burner. Furtherincrease in room temperature closes the secondary contacts 0|6 which,after a predetermined short period of time turn olf the main valve byopening the three-way valve switch TWVS and thereby actuate thethree-way valve 'I'WV to its normal position. These operations areperformed with a relatively small amount of change in room temperature,the room thermostat being preferably very sensitive to temperaturechanges.

From the foregoing description it will be obvious that the rst demandfor heat by the room thermostat opens the modulating gas valve to itsfully modulated position (minimum position as determined by the stop 52)and any additional demand of the room thermostat for heat in the spacebeing heated reduces the heat applied to the bimetal |04 of themodulating pilot valve by the heater |08 and results in opening themodulating gas valve to a further open position. The modulating heater I8 cooperates with the room thermostat in such manner as to vary thefrequency and periods of energization of the heater |05 and in actualpractice the room thermostat contacts cycle rather rapidly so that theamount of heat affecting the bimetal |04 of the modulating pilot valve,even though it is caused by impulses of varying amounts and duration ofcurrent energizing the heater |00, averages out to a certain valuedepending on the effect of the room thermostat upon the circuit.

The room thermostat part of the modulating circuit may be considered asa sender and the heater |06 as a receiver in which the sender, undercertain conditions, may cycle at a rate for example of one second on andtwo seconds olii This rate will vary to greater or lesser proportions ofthe time on as indicated by the tem perature of the surroundings whichaiect the bimetal H and also the voltage as applied to the circuit. Thereceiver may be, however not necessarily is, of somewhat greater massthan that of the sender and the response will be that indicated by anintegration of the on and oi timing of the sender. In actual practice, Ihave found that the receiver is very smooth in operation even thoughsudden changes are transmitted to it by the sender, and also isrelatively quick in its response to any changes by the sender as itresponds to roomtemperature changes.

The room thermostat is a two-stage type in which the contacts closingrst are those which supply current to the modulating pilot valve whichin turn controls the modulating gas valve, this valve being the mainvalve between the gas supply and the burner. The contacts that closesecond are for controlling the on and oi' posi tions of the main valveso that in a certain temperature range the main valve is modulatedbetween minimum ilame position and maximum opening, but at a slightlyhigher temperature is cut olf entirely. Then when the room thermostatagain calls for heat, the secondary contacts open first to turn thevalve on to its minimum modulating position and thereafter the primarycontacts and the modulating heater` I8 cooperating therewith control themain valve in modulating manner.

My disclosed modulating gas heating control is a comparatively simplearrangement of two pilot valves for a modulating gas valve in which oneof the pilot valves effects the on-oi control of the gas valve and theother effects modulation thereof. The pilot valves are controlled in asimple yet effective manner by a two stage thermostat having therein themodulating heater I3 to secure the desired cycling of the roomthermostat to eiect primarily modulation and secondarily modulation ofthe gas Valve under the control of the pilot valves.

The three-Way valve TWV is preferably of the snap acting type and isprovided with a manual reset mechanism 82-84, 85, 85, 88 so that themodulating gas valve can be opened under manual control by pressureinwardly on the reset knob 36. This causes the ange 84 to ride over thehump 85 and move the valve disc 66 to the nonmormal position (seatedagainst the valve Sil). Thereupon the gas in the chamber 50 is reducedthrough the bleed-off passageway 'i8 for permitting the pressure underthe diaphragm 42 to open the valve to its modulating position againstthe action of the spring Thereafter when current ilows in the heater 80,the bimetal 18 will warp downwardly for releasing the hump 85 from theilange 84 and the spring 88 will return the manual reset to its normalposition and permit subsequent automatic operation of the three-wayvalve in the normal manner.

The modulating gas heating control herein disclosed is in some respectssimilar to that disclosed in the copending application of Paul Penn,Ralph S. Penn and myself, Serial No. 222,168, filed April 21, 1951, bututilizes a diierent room thermostat arrangement for closer modulatingcontrol of the heater |06. The room thermostat in the presentapplication includes the modulating heater I8; whereas in the copending'application referred'to, an accelerating heater for the bimetal H was'Yused. The claims hereto appended vare drawn to this differenceinconstruction and'operation of the control.

Some changes may be made in the construction and arrangement of theparts of my modulating gas heating control without departing from thereal spirit and purpose o f my invention, and j it is my intention tocover by my claims any; modined forms of structure or use of mechanicalequivalents which may be reasonably included within their scope. 1

I claim as my invention:

l. In a modulating gas heating control, a mod-A"l ulating gas valvehaving an on-off seat, a modulating seat, an interseat chamber betweensaid seats and a valve plug in said chamber to coact with said seats, afirst diaphragm dividing the valve body into rst and second chambers, asecond diaphragm isolating said rst chamber from said valve seats, astem connection between said valve plug and said diaphragms, restrictedpassageway means continuously supplying gas to said rst chamber, amodulating pilot valve connecting said rst chamber with said secondchamber, an electrically operated actuating mechanism therefor, athree-way valve for connecting said second chamber to either saidrestricted passageway means for admitting gas thereto to close saidvalve plug on said on-oi seat or for exhausting gas therefrom to opensaid valve plug relative to said on-off seat, an electrically operatedactuator for said three-way valve, a room thermostat having primary andsecondary contacts, means for varying the position of engagement of saidprimary contacts, said primary contacts closing ahead of said secondarycontacts on temperature rise affecting said room thermostat, saidprimary contacts being in circuit with said modulating pilot valveactuator to energize it when a circuit is established by closure of saidprimary contacts upon the room thermostat respending to room temperaturerise and to thereby Close said modulating pilot valve to permit increaseof pressure in said iirst chamber from said restricted passageway meansto move said valve plug toward said modulating seat for reducing gasflowy through said gas valve, said means for varying the position ofengagement of said primary contacts comprising a heater in series withsaid primary contacts so as to be energized when they are-closed and awarp element carrying one of said primary contacts and moving ittowardopen position when heated, and said secondary contacts being incircuit with said three-way valve actuator to cause said three-way valveto connect said second chamber to said restricted passageway .means andthereby eiect closure of said valve Aplug on said on-oilc seat.

2. A normally closed modulating gas valve having an on-oi seat, amodulating seat, an interseat chamber between said seats and a valveplug in said chamber to coact with said seats, a rst diaphragm dividingthe valve body into rst and second chambers, a ksecond diaphragmisolating said rlrst chamber from said valve seats, a stem connectionbetween said valve plug and said diaphragms,' passageway meanscontinuously ysupplying gas to said first chamber, a modulating pilotvalvevconnecting said first chamber with said second chamber, anelectrically operated actuator therefor, a three-way valve forconnecting said second chamber to either said passageway means foradmitting gas thereto to close said valve plug on said on-oi seat or forexhausting gas therefrom to open said valve plug relative to said on-oiseat, said three-Way valve being normally in the first position, anelectrically operated actuator for said three-way valve for causing itto connect said second chamber to the burner when the actuator isenergized, a room thermostat having primary and secondary contacts, saidprimary contacts closing ahead of said secondary contacts on temperaturerise affecting said room thermostat, a bimetal element supporting one ofsaid contacts and moving it toward circuit opening position when heated,a heater for said bimetal element, said primary contacts being incircuit with said modulating pilot valve actuator to energize it when acircuit is established through said room thermostat upon the sameresponding to temperature rise and to thereby close said modulatingpilot valve to permit increase of pressure in said rst chamber from saidpassageway means to move said valve plug toward said modulating seat forreducing gas flow through said gas valve, said heater being in serieswith said primary contacts so as to be energized when they are closed,and means for connecting said secondary contacts in circuit with saidthree-way valve actuator, said last means comprising a thermalresponsive switch for energizing said three-way valve actuator and aheater controlled by said secondary contacts of said room thermostat andoperable to open said thermal responsive switch.

References Cited in the iile of this patent UNITED STATES PATENTS NumberName Date 2,263,574 Gille Nov. 25, 1941 2,285,913 Derrah June 9, 19422,328,279 Jones Aug. 31, 1943 2,490,420 Davis Dec. 6, 1949 2,587,733Jones Mar. 4, 1952 FOREIGN PATENTS Number Country Date 711,150 FranceJune 23, 1931

